Staphylococcus aureus Foodborne Illness

Foodborne Intoxications

• Foodborne intoxication occurs when a food containing a preformed toxin is ingested, resulting in poisoning.
• Two types of foodborne intoxications are discussed: staphylococcal intoxication and botulism.
• General characteristics of food poisoning include:
  • The toxin is produced by a pathogen while growing in a food.
  • A toxin can be heat labile or heat stable.
  • Ingestion of a food containing active toxin, not viable microbial cells, is necessary for poisoning (except for infant botulism).
  • Symptoms generally occur quickly, as early as 30 minutes after ingestion.
  • Symptoms differ with type of toxin; enterotoxins produce gastric symptoms and neurotoxins produce neurological symptoms.
  • Febrile symptoms are not present.

Staphylococcal Intoxication

• Importance:
  • Staphylococcal food poisoning is one of the most frequently occurring foodborne diseases worldwide.
  • It was implicated in many outbreaks in the US before the 1980s, but the number of outbreaks has declined in recent years.
• Characteristics of Staphylococcus aureus:
  • Organisms:
    • Gram-positive cocci, nonmotile, noncapsular, and nonsporulating.
  • Growth:
    • Most strains ferment mannitol and produce coagulase, thermonuclease, and hemolysin.
    • Cells are killed at 66°C in 12 minutes, and at 72°C in 15 seconds.
    • Facultative anaerobes, growing rapidly under aerobic conditions.
    • Can ferment carbohydrates and cause proteolysis by extracellular proteolytic enzymes.
    • Grow at relatively low Aw (0.86), low pH (4.8), and high salt and sugar concentrations.
  • Habitat:
    • Enterotoxin-producing Sta. aureus strains are associated with staphylococcal food intoxication.
    • Naturally present in the nose, throat, skin, and hair of healthy humans, animals, and birds.
• Toxins and Toxin Production:
  • Enterotoxigenic strains produce seven different enterotoxins: A, B, C1, C2, C3, D, and E.
  • Heat-stable proteins, differing in toxicity.
  • Normal temperature and time used to process or cook foods do not destroy the potency of the toxins.
  • Optimum growth occurs at 37 to 40°C.
  • Toxins can be detected when a population has reached over a few million per gram or milliliter of food, generally in 4 hours.
• Disease and Symptoms:
  • Staphylococcal toxins cause gastroenteritis, with symptoms occurring within 2 to 4 hours.
  • Symptoms include salivation, nausea, vomiting, abdominal cramps, and diarrhea.
  • Secondary symptoms include sweating, chills, headache, and dehydration.
• Food Association:
  • Many foods have been implicated in staphylococcal foodborne outbreaks, including corned beef, salami, barbecued meat, salads, baking products, and cheeses.
  • Three major contributing factors in outbreaks were improper holding temperature, poor personal hygiene, and contaminated equipment.
• Prevention (Reduction) of the Disease:
  • Impossible to produce foods that are free of Sta. aureus.
  • Prevention involves proper handling, cooking, and storage of foods to prevent growth and toxin production.

Botulism

• Importance:
  • Botulism results from consuming food containing the potent toxin botulin of Clostridium botulinum.
  • It is a neurotoxin, producing neurological symptoms along with some gastric symptoms.
  • Unless prompt treatment is administered, it is quite fatal.
• Characteristics:
  • Organisms:
    • Cells of Clostridium botulinum are... (incomplete sentence)

Test your knowledge about Staphylococcus aureus, a leading cause of foodborne illness. Learn about its growth, habitat, and characteristics.